Every signature is tricky ... and i'm almost sure that David his signed set came from an auction house. Because i remember the set to be stolen in a Hilton hotel and then recovered later. It was taken by an employee instead of sending it. I'll post more on the David Miller set once i get news from him about it.

Before any such acquisition, eBay (especially) or not, one should contact the seller and ask for a letter of provenance. If they can not or will not provide one, pass on the item. If the provenance is incomplete or suspect, pass on the item. That letter is critical to prove its authenticity and its value. When you have an authentic item, you hold something that the man held, and it doesn't matter how much you paid (at least for us Tolkien enthusiasts). When you buy a fake, it doesn't matter how little you paid for it. So be cautious and take your time. There will "always" be another such item to consider purchasing.

Here is my experience with a signed item:

I acquired a 1974 calendar signed by the professor. I know, "He passed away in September 1973". However, the calendar was issued in August 1973. I asked for and received a detailed explanation before the auction and a personalized and absolutely wonderful letter from the seller after. You may read it and check out his signature (and a short inscription) on my website:

I agree with Parmastahir's comments and that you have a real signed calendar with good provenance, but the issue is that a lot of signed items have no provenance and that Tolkien's signature is very easy to fake and adds considerable value to a signed item.

Consider this scenario, I have a early 'Fellowship of the Ring' which I could sell for about £50-100 on Ebay. If I wanted to get a lot more money for this then I could do the following.

Look for names of Professor's in Oxford who were there at the same time as Tolkien and who are no longer alive, Fake a letter from one of their relatives stating that Tolkien had signed the book for this Professor who he knew at Oxford, and insert a fake signature into my book.

If this came up for sale, how would you know if it was authentic. At the moment Forger's do not appear to go to this much trouble, witness the Seymour Hobbit Forgery, as people are still trusting when it comes to signatures and believe that they are genuine.

As well as collecting Tolkien books, I also collect Stamps. For a long time Stamps have suffered from Fakes, Forgeries, Varieties being manufactured, such as cutting out the centre of a stamp and reversing it and sticking it all back to together. I have some postally used German stamps which are probably 90% forgeries.

To get round this, if I want to sell an expensive stamp, each county in the world has an expertising service, where you can send the stamp to a committee, usually at least three recognised experts, who will check and either authenticate the Stamp or state that it as a fake, for a small fee.

This is probably the long term solution for Tolkien signatures as well.